A. Field of the Invention
The present invention relates generally to imaging in the terahertz (THz) frequency range, and, more particularly to a system and method for terahertz imaging that utilizes a single terahertz detector.
B. Description of the Related Art
A terahertz (“THz”) detector or receiver detects electromagnetic energy or radiation with frequencies in the terahertz range (fractions to tens of terahertz, where terahertz=1012 Hertz). A typical THz system consists of a THz transmitter and a THz detector. The transmitter transmits a THz beam that passes through or reflects from an object under examination. The THz detector detects the THz energy that passes through or reflects from the object, and reaches its collecting area over time. Such a system may be considered a 1×1 array or a single pixel system. The significance of this description can be seen by, for example, a digital camera that is characterized by its number of pixels. Each pixel of the camera is just a single detector capable of detecting electromagnetic energy in the visible wavelength. To obtain an image of a large area having good spatial details (resolution), a large array of detectors is needed in the imaging system. This is why a digital camera with more pixels has better resolution (e.g., a clearer and sharper picture) and costs more.
The same principle applies to THz imaging. Conventional THz systems detect THz energy over a certain area defined by the size of a THz beam. With a single THz detector (one pixel), a tradeoff needs to be made between the size of the imaging area and the spatial resolution. This is because the energy from different parts of the imaging area arrives at the single THz detector about the same time, and cannot be separated to get spatial details. To obtain good spatial resolution with conventional THz systems, the THz beam must have a small beam size, which reduces the area that can be imaged. To image a larger area, the small THz beam may be scanned over the area to be imaged or the area is scanned across the THz beam. To date, the only known way to create a THz array imager is to utilize an array of THz detectors. Unfortunately, it is very difficult and expensive to fabricate an array of THz detectors for a THz imaging system.
Thus, there is a need in the art for a single terahertz detector imaging system that detects an image of a large area and provides good spatial details (high resolution) without the need to scan a THz beam across an entire sample or scan the entire sample across the THz beam.